1. Field of the Invention
The present invention relates to an apparatus for stretching, loosening and fixing a wire member such as PC (prestressed concrete) steel wires or the like so that specified compression stress is applied to a structure made of concrete.
2. Description of the Prior Art
There is conventionally known a wedge fixation method for stretching and loosening PC steel wires. According to this method, with the use of a jack capable of simultaneously stretching a PC steel wire and pushing a wedge, a PC steel wire is stretched and a steel wedge is then pushed into a wedge housing space in a fixing member to fix the PC steel wire therein. In order to finely adjust the tension of the PC steel wire after completion of such fixation, it is required to slightly pull out the wedge thus pushed into the wedge housing space, from the wedge housing space for relieving the PC steel wire of the tension. However, at the time the PC steel wire is loosened, the wedge is pushed into the fixing member due to frictional force, thereby preventing the PC steel wire from being loosened and fixed. Special fixing means are therefore required in addition to the jack. Accordingly the number of required devices is therefore increased, thus disadvantageously decreasing working efficiency and safety.